The present invention relates to an intraocular insert for implantation in the interior of the human eye and, more particularly, to an intraocular implant with at least one mirror.
Macular degeneration is a disorder in which the central retinal area (the macula) degenerates, e.g., because of age (age-related macular degeneration, or AMD), diabetic retinopathy, ocular vascular accidents or diseases, retinal dystrophies (such as, for example, cone dystrophy), central nervous system (CNS) diseases, etc. These disorders in the macular area cause difficulty in central vision such that the afflicted person finds it difficult to read, drive, or perform other daily activities that require fine, sharp, central vision, but the individual's peripheral vision remains unaffected.
The normal eye usually functions in a manner such that central vision is used for focused vision, such as with reading, for example. The extraocular muscles move the globe of the eye so as to adjust the eye so that the image of an object being looked at impacts always on the point of central vision that occupies only a small fraction (less than 10%) of the retina, that is, the macula. The bulk of the retina is used for peripheral vision, which serves primarily for orientation in space and the visual acuity is not as sharp as that of the central vision of the macula. Thus central vision provides a relatively small field of view with very high resolution for perception of details, while peripheral vision provides a wide field of view with relatively low resolution, providing sufficient information for navigation and detection of targets of interest.
AMD is a common cause of visual loss among people over the age of 60. The risk of developing AMD is nearly 30% in those over age 75.
Low vision aids such as special telescopic or microscopic eyeglasses that create a magnification of the object on the retina have been used in the treatment of this condition. However, when an outside telescope is used, the visual field is very narrowly restricted, and therefore the afflicted person has to move his or her head back and forth to follow the lines being read. An alternative has been an intraocular implant containing a telescope (as described in Applicant's U.S. Pat. No. 5,354,335, U.S. Pat. Nos. 5,391,202, 5,814,103, 5,876,442, 5,928,283, 6,007,579 and 6,066,171). Laser photocoagulation and photodynamic therapy, as well as vitamin supplements, are also used in the treatment of this condition. Limitations to the use of the intraocular implants with a telescope include that these implants can not be used in both eyes—one eye (the implanted eye) is needed for improved central vision and one (the other eye, without the implant) for peripheral vision. The IOL with the telescope (also known as an implantable miniaturized telescope, or IMT) obscures peripheral vision and interferes with the pupillary opening. The IOL with the telescope has a black posterior part that does not allow light to enter the eye, except through the telescope, as that would cause stray light and glare. The pupil has to be narrowed so that the pupil covers at least some of the black part of the IMT. With use of the IOL with the telescope there is a considerable reduction in the amount of light that enters the eye. It is reduced by up to 9-fold for a 3× magnification, (that is, only {fraction (1/9)} of the light enters the eye), depending on the size of the opening of the telescope's cylinder. Further, there is a limit to the amount of magnification permitted by the geometry and the size of the telescope so that one can not achieve higher magnification without further restricting the visual field. Furthermore, use in only one eye causes anisoconia with a difference in image size between the eyes. In addition, retinal treatment such as laser or photodynamic therapy is difficult to perform through an IOL with a telescope.
In addition, it would be desirable to have an intraocular implant that could be adapted so as to be used for treatment of other diseases and problems of the eye. For example, such an intraocular implant could be used for treatment of diseases and processes that cause constriction of peripheral vision, including inherited retinal disorders causing retinitis pigmentosa, and glaucoma as examples. Further applications for such an intraocular implant include increased image magnification, increased illumination and the elimination of certain wavelengths of light, such as ultraviolet light, as well as allowing depth perception with vision from a single eye by creating monocular stereopsis. An implant providing increased illumination and increased magnification would be desirable also for use in the treatment of regular cataract patients, who do not have retinal problems.
U.S. Pat. No. 4,759,761 to Portnoy discloses a catadioptric intraocular lens containing interior mirrored surfaces forming a folded telescope. The lens of the Portnoy patent suffers from many limitations similar to those of the IMT discussed hereinabove. In particular, the lens disclosed in U.S. Pat. No. 4,759,761 does not preserve and permit peripheral vision because the mirrors cover the entire pupillary aperture it does not preserve the full peripheral visual field. It would be desirable to have a device that increases central visual field but as well allows normal peripheral vision. The device of the Portnoy patent produces a limited magnified central visual field only. It would be desirable to have a device that permits a full normally sized visual field with a magnified central image for seeing precise objects such as for reading while preserving peripheral vision, without magnification, or with very small amounts of magnification, as well. Further, the device of the Portnoy patent is not structured so as be useful for other disease processes such as diabetic maculopathy, retinitis pigmentosa or advanced glaucoma. As the mirrors cover the entire pupillary aperture, it tries to achieve a maximal increased central image visual field while covering and obscuring the natural peripheral visual field and thus it is almost impossible to examine the retina or treat it, beyond the blockage of peripheral vision. As for the IMT with telescope, the device of Portnoy, which was never built or used in clinical practice, can only be implanted in one eye. This leads to several limitations including: anisoconia (difference in image size between the eyes); a difference in the angular velocity of moving objects between the eyes; and the need for prolonged rehabilitation due to the two eves having different visual performance: one eye for a magnified central visual field and the other for the normal peripheral visual field. Further, if, in the future, one eye severely deteriorates the patient cannot function with his only eye as he can see only either central vision or peripheral vision, but not both, with the device of Portnoy. The device of Portnoy has only two mirrors, which are concentric; it would be of benefit to have a device with more than two mirrors, as well as an implant in which the mirror was not necessarily a ring, and with different openings that disturbed the peripheral vision less.
There is thus a widely recognized need for, and it would be highly advantageous to have, an intraocular implant for treatment of defects in central vision, including AMD and other disorders of the macula, as well as increasing the central visual field while preserving peripheral vision, and other disorders of vision, such as regular cataracts, while preserving the natural unchanged peripheral visual field, devoid of the above limitations.